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Scala example source code file (State.scala)

This example Scala source code file (State.scala) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Scala by Example" TM.

Learn more about this Scala project at its project page.

Java - Scala tags/keywords

indexedstate, indexedstatefunctions, state, unit

The State.scala Scala example source code

package scalaz

trait IndexedStateFunctions {
  def constantIndexedState[S1, S2, A](a: A, s: => S2): IndexedState[S1, S2, A] =
    IndexedState((_: S1) => (s, a))

  def iPut[S1, S2](s: S2): IndexedState[S1, S2, Unit] = IndexedState(_ => (s, ()))

  def iModify[S1, S2](f: S1 => S2): IndexedState[S1, S2, Unit] = IndexedState(s => {
    val r = f(s);
    (r, ())

trait StateFunctions extends IndexedStateFunctions {
  def constantState[S, A](a: A, s: => S): State[S, A] =
    State((_: S) => (s, a))

  def state[S, A](a: A): State[S, A] =
    State((_ : S, a))

  def init[S]: State[S, S] = State(s => (s, s))

  def get[S]: State[S, S] = init

  def gets[S, T](f: S => T): State[S, T] = State(s => (s, f(s)))

  def put[S](s: S): State[S, Unit] = State(_ => (s, ()))

  def modify[S](f: S => S): State[S, Unit] = State(s => {
    val r = f(s);
    (r, ())

Other Scala examples (source code examples)

Here is a short list of links related to this Scala State.scala source code file:

my book on functional programming


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